Roth was one of a group of GalSec colonists stranded on Earth after their ship was destroyed while answering a fake distress signal. Styre performed cruel experiments on him to assess human physical limitations. These experiments caused severe mental anguish, to such an extent that he went half-mad.
He temporarily escaped his captor, his right arm badly burned and mind quite troubled. Roth found Sarah Jane wandering out in the open and protected her from being found by Styre's robot that was patrolling the area for humans and escaped test subjects to capture, but the robot soon returned and caught them. Roth, rather than face another experiment, freed himself from the robot's clutches and fled for his life. Styre took out a blaster and shot him before he could escape. Roth dropped dead, making little ground away from his would-be captor. Sarah responded with anger at his act of murder, but Styre replied that this was his function as a warrior, insultingly calling Roth a moron who was of no further use to him after being tested already. (TV: The Sontaran Experiment)